The invention herein described relates generally to brakes and methods, more particularly to brakes and methods using electromechanical actuators, and still more particularly to electrically actuated aircraft brakes and methods.
Aircraft wheel and brakes heretofore have included a non-rotatable wheel support, a wheel rotatably mounted to the wheel support, and a brake disk stack having alternating rotor and stator disks mounted with respect to the wheel support and wheel for relative axial movement. Each rotor disk is coupled to the wheel for rotation therewith and each stator disk is coupled to the wheel support against rotation. A back plate is located at the rear end of the disk pack and a brake head is located at the front end. The brake head may house a plurality of actuator rams that extend to compress the brake disk stack against the back plate. Torque is taken out by the stator disks through a static torque tube or the like.
Electrically actuated aircraft brakes of various configurations are known, as exemplified by U.S. Pat. Nos. 4,381,049, 4,432,440, 4,542,809 and 4,567,967. The brakes shown in these patents include electric motors which respond to an electrical control signal to effect rotation of a ring gear member which interacts through a plurality of balls to drive a linearly movable ram member into contacting engagement with a brake disk stack to effect compression thereof and braking of a wheel.
In U.S. Pat. No. 4,596,316, another configuration of an electrically actuated brake uses a roller screw drive wherein a ring gear member interacts through a plurality of roller screws to drive a ram member into engagement with a brake pressure plate to effect compression of the brake disk stack for braking action. A plurality of electric motors and their associated pinions drive a ring gear into rotation and the plurality of roller screws effect linear axial movement of the ram member.
In U.S. Pat. No. 4,865,162, a further electrically actuated aircraft brake employs a roller screw drive mechanism driven by an electric torque motor through a gear drive associated with either the screw or the nut of the roller screw drive mechanism. Rotation of the gear drive by the torque motor moves the other one of the screw or nut into axial engagement with a brake disk stack to compress the stack for braking. A plurality of the roller screw drive mechanisms and respective gear drives and torque motors are assembled in a brake head in a balanced arrangement about the axis of the wheel to apply and release a brake pressure force on the brake disk stack in response to an electrical control signal to the torque motors.
The repair or maintenance of these presently known brakes including torque motor driven rams heretofore has required significant disassembly of the brake. The complex integrated nature of prior art designs normally require substantial teardown of the assembly for maintenance, repair and/or overhaul of the assembly even if minor repair or only replacement of a single faulty component is required. Associated with extensive teardown is a lengthy reassembly and retest procedure to verify flight worthiness. Also, a highly integrated design and assembly with complex machining and assembly procedures is costly to process and manufacture. Distribution and parts stocking of individual components of such an assembly is similarly complex and inefficient as cam be appreciated by those knowledgeable in this area. Consequently, an aircraft, for example a commercial passenger aircraft, would most likely have to be taken out of scheduled service until a faulty actuator could be serviced. This results in lost revenue for the airline, scheduling adjustments, considerable inconvenience for customers, etc.
The present invention provides a brake and method characterized by the use actuator modules each of which can be easily and quickly replaced as a unit. This enables quick and easy replacement of the actuator modules preferably without requiring disassembly of the overall brake and wheel assembly. Also, it is conceivable that a malfunctioning actuator module could be replaced on an aircraft and tested with a minimum of equipment preferably quickly enough to allow the aircraft to remain in scheduled service and/or with a minimum of downtime. In addition, periodic maintenance of the brake can be done quicker and more efficiently by replacing the actuator modules with reconditioned and/or new actuator modules.
Accordingly, a preferred embodiment of a brake according to the present invention comprises a brake disk stack, a brake head, and at least one actuator module mounted to the brake head. The actuator module includes a module housing, a reciprocating ram and a motive device operatively connected to the reciprocating ram for selectively moving the reciprocating ram into and out of forceful engagement with the brake disk stack for applying and releasing braking force. In accordance with the invention, the actuator module is removable as a unit from one side of the brake head.
Further in accordance with a preferred embodiment of the invention, the actuator module is removable from the brake head from the side thereof opposite the brake disk stack and the ram is guided in the module housing for movement toward and away from the brake disk stack. The ram includes a ram nut, and the motive device preferably includes an electric motor drivingly connected to a lead screw (preferably a ball screw although other type of screw drives ant the like are contemplated) in threaded engagement with the ram nut whereupon rotation of the lead screw effects linear movement of the nut toward and away from the brake disk stack. The ram nut preferably is guided in the module housing for movement toward and away from the brake disk stack. To this end, the module housing includes a guideway for guiding the ram nut, and the guideway and ram nut respectively have polygonal cross-sections defined by plural outer side surfaces which rotationally interfere with one another to restrain rotation of the ram nut relative to the housing.
In a preferred application, the brake is used in combination with an aircraft wheel assembly.
According to another aspect of the invention, there is provided a method for servicing the aforesaid brake. The method comprises the steps of identifying a brake module to be replaced, and removing and replacing the identified brake module with another brake module without disassembly of the brake disk stack. Preferably, when the brake is part of a wheel and brake assembly, the removing and replacing step includes removing and replacing the identified brake module without removal of the wheel from the wheel and brake assembly.